Throwing light

This exercise is for four or more players.

Two players secretly decide upon a topic of conversation.

They then begin discussing the topic in the presence of the other players. Their Point of Concentration is to mislead the others as to the identity of the topic they are discussing. They may not use any false statements during their discussion. The other players may not ask questions nor guess the topic
aloud. But when a player thinks he knows what the topic is, he is to join in the conversation. At any time after he has joined in the conversation, he may be challenged. When this occurs, he must whisper what he thinks the topic is to one of the two conversation leaders. If he has guessed correctly, he continues to participate
in the conversation. If he is incorrect, he is one-third out of die game and must become an observer again until he has a new guess and rejoins the conversation.

A player may join inthe conversation for some time without arousing suspicion and being challenged.
The game goes on until all the players have either guessed correctly and joined the conversation or have made three wrong guesses and are out of the game.

References

From the Book: Viola Spolin - Improvisation for the theater